Classifier units for friable material pulverizers



July 24, 1951 CLASSIFIER Filed Aug. 20, 1945 H. G. LYKKl-:N ETAL 2,561,388

UNITS FOR FRIABLE MATERIAL PULVERIZERS July 24, 1951 H. G. LYKKEN ETA. 2,561,388

CLASSIFIER UNITS FOR FRIABLE' MATERIAL PULVERIZERS Filed Aug. 20, 1945 5 Sheets-Sheet 2 f/gz.

July 24, 1951 H. G. LYKKEN TAL CLASSIFIER UNITS FOR FRIABLE MATERIAL PULVERIZERS Filed Aug. 20, 1945 5 Sheets-Sheet 3 July 24, 1951 H. G. LYKKEN Erm.

CLASSIFIER UNITS FOR FRIABLE MATERIAL PULVRIZERS 5 Sheets-Sheet 5 Filed Aug. 20, 1945 Figc /Z Patented July 24, 1951 CLASSIFIER UNITS FR FRIABLE liIATE- RIAL PULVERIZERS Henry G. Lykken and William H. Lykken, Minneapolis, Minn., assignors to The Microcyclomat Co., Minneapolis, Minn., a corporation of Dela- Ware Application August 20, 1945, Serial N0. 611,512

5 Claims. l O'ur invention relates to new and improved constructions of classifier units for use With machines for pulverizing friable materials.

This application is a continuation-in-part of our co-pending application Serial No. 498,988,'

filed August 17, 1943, now Patent No. 2,497,088, issued February 14, 1950.

' In Patents No. 2,294,921 issued vSeptember 8,

1942, and No. 2,304,264 issued December 8, 1942,

various forms of unitary machines for pulverizying and classifying materials are shown. From time to time improvements have been made in the portion of the machine having to do with pulverizing the materials but in all cases pulverization is by means of a vortex of airor iluid- `suspended material in which reduction in particle size is by impact and attrition of particle upon particle; and in all cases the sufficiently pulverized material is removed from the pulverzing zone by means of a current of air introduced at the bottom of the pulverizing vortex and flowing therethrough in the direction of the axis of the vortex to thereby lift the pulverized material out ofthe vortex and into an upper classifying zone. Inthe latter zone the pulverized material has been subjected to a different vortical action and to the same cross current of air by means of which the suiciently pulverized material has been delivered from the machine and the oversize particles have been rejected and fall by gravity back into the pulverizing zone for further vreduction in particle size. One of the great problems in the classifier zone has been to prevent oversize particles from escaping from the machine along with the desired material, thereby spoiling the classification. The improvements described and claimed in the present application are addressed to curing that difficulty, and the same have been used successfully in practice.

Another object of our invention is to considerably simplify the construction of the classifier portion of the machine.

A further object of our invention is to provide a classifier with means to stop stray oversize particles of material from escaping over the top of the rotor therein.

A further object of our invention is tovprovide classifier mechanism Which may be readily ychanged and adapted to give the same improved results with a Wide variety of materials. That is to say, the classifier mechanism has to be rearranged to function properly according to the nature of the material being pulverized and classifled, as Well as to the desired size of delivered particle. A material which is light in Weight and the fractures of the particles of which are deflnite and more or less uniform in dimensions will require a vdifferent classifier mechanism yfrom material even of the same specific gravity but in which the fractures are irregular and the particles are ilakelike. Again, the classifier mecha'- nism must be altered according to the different specific gravities of materials and according to the degree of tendency of the particles to cohere or coalesce after pulverization thereof. In fact, every characteristic of a material must be taken into consideration and the classifier mechanism of this application is arranged to be readily adaptable to give uniformly good results with all friable materials.

Because of these variable factors it is not possible to select one embodiment as the best mode of applying the invention. Each is the best mode for its particular material and conditions.v By describing several embodiments the principles of the invention are illustrated so that the adaptation thereof Will be fully understood. I

Heretofore, in most cases, classifier devices have depended upon the action of rotors having Ablades which are flat-sided and of greater height than width to set up a classifying Vortex, especially within the rotor. Such rotors do not create or maintain a wholly smooth and uniform vortex, since each blade moves a quantity of air, proportional to its size, thereby producing an undulating effect in the vortex, and each blade as it passes through the air necessarily produces a vacuum in back of the blade. Air rushes into this vacuum area around the edges of the blade and as a result a considerable number of eddies are created throughout the classification area, all of which conditions disturb the smoothness of the vortex and the classification. For example, oversize material in the vicinity of the rotor blades may be mixed with the desired material and also carried into the eddies and occasionally before the centrifugal effect can eject the oversize, it escapes out of the machine. Our previous designs of classifiers have been improvements over what preceded them and the present invention is a still further improvement.

We have discovered that a more universally applicable classifier producing more uniform results is one in which the classifier rotor, in its simplest form, is made up of equi-spaced round spokes of small diameter, preferably located in juxtaposition to the outlet from the machine and at the top of afree space into which the material to be classified is introduced. Such a rotor sets up a minor centrifugal action Within the rotor,

and by reason of its high speed creates and maintains a useful vortex of air and suspended material in a region or free space below the rotor. The curved advancing and retreating surfaces of the round spokes create no undulations or eddies which will disturb the vortex action so that the centrifugal action of the vortex will be effective in rejecting a greater percentage of oversize particles. through the classifier rotor by the suction of a fan, adjusted according to the particle size, etc., of the material, so that the rotor spokes are in effect combing through the air and material at high speed, and the curved 'advancing faces of the spokes as well as the broad width thereof strike the remaining oversize material and deect it away from the rotor before it has a chance to escape through the rotor, but the current of air will carry out the material which is'of the proper size. As will beexplained, the diameter of the spokes may vary slightly, and the number .thereof also will be 'selected according to the delivered particle size. The finer the particle size the greater willibe the number of spokes.

Also, stray oversize material Vheretofore has crept up the wall of the machine and 'over the top of the rotor, thereby reaching the outlet without being subject to the action ofthe rotor. `In some cases a special sealing ring 'arrangement will 'be effective, but we 'have vfound the most effective construction generally to be one in which the rotor includes a flared skirt extending downwardly'from the edge of the outlet opening and .haring outwardly toward 'the wall of the casing. Such a skirt, rotating with the high speed rotor, constantly directs a downward current of airand .suspended material against the'wall of the casing which sweeps the complete circumference of the casing and dislodges any material on the wall, while its angular component'forces the material awayfrom the wall Wherefgravity can return the oversize to the bottom of the casing. With this skirt arrangement, no special sealing ring, etc.`

is needed.

To meet the great variety of conditions in which it is desirable ito use these machines, it is at vtimes best -`to use 'two vor more classifier rotors, either' closely spaced and operating as a unit, or spaced apart and operating more or less :independently of each other.

Other .and further objects of our invention will be understood from .this specification taken in conjunction with the accompanying drawings, in which- Figure 1 is a central Vertical section of a unitary pulverizing and classifying Vmachine constructed according to our invention.

Fig. 2 is a central vertical section of a sepa- `rate classifier unit, according to our invention,

trating one manner of altering the classier rotor for use with `smaller particle sizes than the rotor of Fig. 3.

Figs. 5 and 6 are fragmentary views similar -to Figs. 3 and 4 respectively and illustrating one manner of using two classifier rotors operating l Aas a unit.

Fig. 'l is a fragmentary view of another form of double rotorrclassifier mechanism.

Fig. 8 is a -partial 4vertical sectional View of a The desired material is withdrawnfloor of the pulverizing chamber.

unitary pulverizing and' classifying mechanism illustrating the use of separated somewhat independently operating classifier rotors of our improved construction.

Fig. 9 is a partial plan view of the rotor of Figs. 3 and 4, on the line of 9-9 of Fig. 1 and is illustrative of the plan View of all the rotors.

Fig. 10 is a vertical sectional View illustrating the simplest form of the new classier rotor.

Fig. ll is a view similar to Fig. l0 illustrating thefapplication of a special sealing ring which vmay be used with the rotor of Fig. l0.

Fig. l2 is a View similar to Fig. ll illustrating another form of double rotor.

Fig. 13 is a partial View in plan of the rotor of Fig. 12.

While the details of construction and the mode top cover plate 2li which is y'bolted to the peripheral flange 25 of 'the enlarged portion of Vthe` cylinder. A rotor shaft 2S is centrally mounted in the cylindrical casing 22 so as to rotatel'in the upper bearing'2l and the lower 'bearing'28, respectively carried by the cover Aplate'and base. The lower end oi' shaft 25 extends into the hollow base 2i and there carries a sheave 29 through which the 'shaft is driven at high speed from the motor v3l that is mounted on the 'base with its shaft extending thereinto. The motor shaft carries the sheave 32 which is vconnected to the sheave 3l by driving "belts 33.

Spaced above the base 2l, the cylinder 22 has mounted therein a 'dish-'shaped vmember 34,`hav ing a central aperture 3:5, and constituting the Opening 35 is for the admission of air into the pulverizing chamber and also into Ythe 'classifier chamber, the air being received from the opening 36 vin the side of theA cylinder 22, which opening communicates with the space 'between the base vv2l and the floor 34. The volume'of air admitted through the opening 3'5 iscontrolled in any suitable manner. We have used for this purpose a slide indicated at 31 which is operated from 'outside the cylinder 22 and moves on guideways 31A to regulate the effective area ofthe opening 35.

The shaft .26 has a bottom rotor vdisc 33 fastened thereto which extends horizontally adjacent the oor 3G and is of less diameter than the internal diameter of the cylinder 22. The underside of this disc carries a plurality of short radial fan blades 3Q which 'distribute the Yincoming air uniformly around the casing, the same entering therein around the periphery of the rotor disc 33.

The pulverizing rotor comprises three'superimposed closed-end rotor sections Ill, t2 and 'd'3 which are alike in mechanical construction except that in the illustrated embodiment the sections are progressively smallerin diameter. Each section comprisesahubtwhich'is keyed to the shaft 26 and to the intermediate flange of which is secured the horizontal `disc t5 around `the periphery of which are secured a plurality of equispaced vertical rotor 'blades d$,the radial extent of which isy selected according to the desired spacing between the outer edges thereof and the interior wall of the casing, or a liner therefor, as illustrated. Resting on ltop of each set of rotor blades is an imperforate plate 41 separating the rotor` `sections from each other, the top plate 41 closing the upper end of the top rotor section and also defining the bottom of the classier zone.

Each rotor section sets up a pulverizing vortex of air, and suspended material, in the annular space around each rotor. If the number of blades and the width of the annular space is alike in each section, then each will have similar pulverizing characteristics, but the number of rotor blades in each section and the width of the annular space opposite each section can be selected according ,to the nature of the material being pulverized, to thev end that the most eicient operation may be had in each case.

Material to be pulverized is fed into the casing continuously through the opening 5I located at cr near the top of the uppermost pul'verizing rotor section, the material falling into the pulverizing vortex. The feed of the material is from the hopper 52 by means of the feed screw 53 which is driven from the motor 54, to which it may be connected by sprockets and chain. Any suitable means may be used for regulating the speed of the :feed screw to maintain the proper circulating load of air-suspended material in the pulverizing zone.

The air admitted through the opening 35 in the floor of the casing 22 passes vertically through the pulverizing vortex and continuously removes the sufficiently pulverized material therefrom, as

rapidly as it is produced. In the illustrated embodiment this 'material is lifted into the free space 56 immediately above the pulverizing rotor section.y The drawing of the air vertically through the pulverizing vortex, and in fact through the classifyingT rotor about to be described,l is by means of the fan 5l located in the enlarged chamber 23 of the casing. This fan comprises a hub 58 keyed to the shaft 25 and carrying horizontal disc 59 around the periphery of which are mounted a plurality of radial fan blades Sii. The capacity of this fan is selected according to the size of the particles to be delivered from the machine, and again the various factors of the material must be taken into con sideration so that the air current will be properly proportioned, as will be understood. Of course, some oversize material will leave the pulverizing zone and enter the classier zone, and such oversize must be kept out of the material lfinally de-` livered from the machine, the same preferably being returned automatically to the pulverizing zone for further reduction in size.

As explained above, the classifying of the material removed from the pulverizing Zone is desirably carried out with some centrifugal action to remove the bulk of the oversize. The classifier comprises the free space 56 at the upper end of which is the classifier rotor, indicated generally by the reference numeral 65. The height of the free space 56 is selective and changes with the material being pulverized and to some extent with the iineness of the particle size. For most materials in which the maximum delivered particle desired is not less than five microns, the free space will be from six to eight inches in height when using a single rotor. The classifier rotor has a hub 6B which is keyed to the shaft 26, and one or more sleeves 51 t about the shaft 26 accoi-ding to the desired height of the free space 56, the 4sleeves resting on top of the top pulverizing rotor plate 41, and the hub `66 of the classifier rotor rests on top of the sleeves 61. i,

The hub G6 has an intermediate flange 68- on which is secured the ring-shaped plate v69 which, with the ange68 Kforms an imperforate center disc closing the center portion of the machinev from the passage of `material outwardly along the shaft 2E and for a substantial distance radially therefrom. A plurality of equi-.spaced round rodsor spokes 'I l (Fig. 3) are mounted on top of the ring 69 and radiate outwardly there,- irom, extending close to the inner wall of the casing 22, or a suitable liner v"Hl thereon,if one is used. A second ring-shaped plate 12 is mounted on the underside of the spokes 1l, the plate 'i2 kextending toand joining the outer ends of the spokes, but being Aspaced from the perimeterv of the inner-ring-plate 69 so as to define the an. nular slot 13, the twoplates being concentric.'y This slot constitutes the outlet opening from .the classifier into the fan chamber 23. Our, ap-

plication Serial No. 367,314 filed November 27, 1940, now Patent No. 2,392,331, issued January 8, 1946, is directedto the provision oi" an annular outlet slot and explains that both the width of the slot and its radial location are selectiveA in accordance with the size of the particle being delivered from the machine. If a wider ring-plate 12A (Fig. 4) is substituted for the one illustrated in lfiig. 3, and the inner ring-plate 69 is notv changed, the width of the annular ,slot '13A will be reduced and its effective radial position will be moved inwardly, with which arrangement the maximum particlesize passing through the opening will be smallerrthan `with the relativeposition and width illustrated in Fig. 1. The variationy in particle size will dependto a considerable eX- tent upon the internal diameter of the ring-plate 'l2 which defines the outer edge ofthe annular slot. The width of the inner ring-plate 69 also may be varied to exercise somewhat similar con-` trol but with the rotor as now constructed, this usually is not necessary. In any event, the spokes 'Il extend across the annular outlet. i

The classier rotor is augmented by the addition of the annular skirt 14 (Fig. 3) vwhich extends from adjacent the outer edge of the outlet slot 13 downwardly and tapers outwardly close to the inner wall of the casing 22. The angle of the downward taper is preferably about 45,7% although it may be varied a few degrees more or less than the angle. Consequently, as the width of the outer ring-plate 12Ais increased the depth of the skirt 14A (Fig. 4) becomes greater in order for it to nevertheless terminate ad-v jacent the inner wall of the casing 22, and as will be explained, this is desirable with the smaller particle sizes which will be allowedto pass through the outlet opening 13A. A diaphragm ring 15 is secured to the bottom of the enlarged chamber 23 and extends inwardly of the `casing 22, the spokes 1| of the classifier rotor operating in close running clearance therebeneath. 'It is desirable, but not essential, that the diaphragm ring be of a width so that its internal diameter is the same as that of the ring-plate 12 ofthe classifier rotor and thus the two inner edges of these elements will be in register, and the ring 15 is readily replaceable.

The functioning of this classifier rotor may be described` as follows: The rotor operates at high speed at the upper end of the classier space and it will cause the air-suspended material to whirl in somewhat of a vortex in the free space 56, the

axis of the shaft 26 being the center of the vorI 7 tex. 1n this ease, however, the rotor 65 produces a smooth, undisturbed vortex action in the `free space because the rotoris Ymade up of iiat elements which are substantially concentric with the classifying vortex, except for the spokes 1l, and they are small in diameter and round. Furthermore, only a relatively small partof each spoke lis exposed to the free space through the annular slot '13. The round spoke, presenting a rounded 'advancing edge, causes very' little displacement -of the air as it passes therethrough and hence the slight undulations or ripples do not disturb the smoothness of the classifying vortex als a practical matter; and likewise the roundedretreating `face of thespoke produces only `mino-r eddies in back oi the spoke. Even theserninor eddies are displaced above the center line oi' the spoke rbecause of the action of the fan'l in withdrawing the air and selected material through the outlet slot 13. Of course, if desired, the spokes 'Il could be streamlined in ac-` cordance with the air now, but we have not found that to be necessary in any instance to date. vA further contributing factor to the smoothness of the vortex action in the space 56 is that the rotor 65 is located at the top of the space, which is of considerable depth.

It will be appreciated that the vortex in the free space 56 vhas a lower peripheral speed than the rotor, but the vortex action will eliminate a large part of the oversize material that was in-l troduced therein along with the material which is of the propervsize. As'the fan 5l' withdraws the air andinaterial of proper size through the annular vslot l'13, the disposition thereof radially' vortex action willbe met by `the spokes TI which, f

at high speed, are cutting through the stream of air and material passing through the annular slot 13. By reason of the'curved advancing edge and the broad basev of each spoke, the stray oversize particles are struck and knocked back' into the f.

free space and may be knocked to the wall of the casing. The oversize `material eventually reaches the `casing wall or wall liner and its speed being there retarded, it falls by gravity back into the pulverizingzone.

AAs was previously explained, other stray oversize particles tend to move upwardly along the casing wall, especially those that are nearly of nearly of the proper size.

thedesired particle size, and by reason of the air v the upward passage of oversize particles in the space outside the classifier rotor by directing a stream of air from ythe underside of the ski-rt, which stream strikes the wall/of the casing, along a vline immediately below the skirt, andl sweeps all particles from the wall at the place of :im-r

pingement. Itis apparent that this is a-continuous action so that .oversize material ltendiiig to enter the space between'theedge of .the rotor and the casing is continually'dislodge and eitherstara ed downwardly out of the classifier zone or, by reason of the angularty of the air stream leaving the skirt, is moved away from the wall and into the classifier vortex. The smaller the particles to be collected, and the lower the specific gravity of the material, the more diiicult it is to separate out the oversize particles which are Thus, the deeper skirt, illustrated at MA, provides a larger zone of .higher speed and greater centrifugal action, andthe deeper skirt also gives a stronger downwardly directed stream of air sweeping the wall and sending the oversize back for further pulverization. Likewise with the flakier particles, the stronger downstream is more effective in dislodging the same from the inner wall of the casing and counteracting its tendency to iloat upwardly.

By a comparison of Figs. and fl, it is believed that the relationships of annular outlet slots and relative depths 0i' the associated skirts will be understood as between that for coarser mate-i rials, shown in Fig. 3, and for nner materials, shown in Fig. 4. It is not intended that these figures of the drawings illustrate the limits in the width of the slot or its radial location, or the depth of the rotor skirt. VAlso, by reference to Fig. 9, Athe relationship of annular slot and the rotorspokes l'l will be understood.

The rods or spokes l'l most generally will have a diameter of one-quarter inch, but they may .be of difierent diameters, and we have used rods live-'eighths of an inch in diameter in very large mills. Also, the number of rods or spokes are selective between sixteen spokes for very coarse material, of the order of rtwo hundred screen mesh, and sixty-four spokes where the delivered particle size is of the order of iive microns, or the material is difficult to classify. In most applications thirty-two spokes is found to be satv isfactory. The above specifications apply to all forms of classiiier rotor described in this application.

The construction of the classifier rotors is completed by the addition of the vertical ring or wall It extending between the outer edge of the horizontal ring-plate l2 and the lower edge of the flared skirt, such as 'lt or MA in Figs. 3 and 4. This rotor wall 'I6 extends parallel to the casing 22V and is spaced only a short distance therefrom. Nevertheless a smooth intense vortex action will be set up in the annular space between the rotor wall 'E6 and the casing, or its liner, to further aid in keeping oversize from Ypassing ybehind and over` the rotor.

It will be understood that in accordance with the usual practice, the desired material, which is withdrawn through the annular outlet i3 `by the fan 5l, will vbe ejected from the machine 'through the delivery outlet il by the action of the same ian. Also, that the fan 5l need not be an integral part of the machine.

The classifier arrangements described in this application are also applicable to other types of pulveriziug machinery, or may be used'as a classifier unit apart vfrom any pulverizing mechanism. Fig. 2 is illustrative oi a classifier unit to -be applied to a horizontal type of pulverizer such as is shown in the patent of Henry G. Lykken No. 1,838,560 issued December 29, 1931, for example. In this embodiment, the casing 8| isin the `shape of a irustrum of an inverted cone, which is open at its top and bottom and is mounted upon a base irame '82. Extending upwardly from the base frame are -a plurality of supporting `arms 83 upon which is secured the rotor housing 84 and the fan housing 85. The structure is closed by the cover plate v86 on which is supported the auxiliary housing 8l. A rotor shaft 88 is centrally mounted to rotate in bearings 2| and B2 respectively supported by the cover plate 85 and the top oi the housing 8l. The shaft 8S is rotated at high speed being driven from the motor 93 through the belt and pulley drive indicated at 94.

The classiiier rotor, indicated at 95 is mounted in its cylindrical housing 8f3, the ysame being keyed to the shaft 88 and extending radially close to the inner wall of the housing 84. The rotor 95 is similar in construction to the rotor 65 described above in4 connection with Figs. l, 3 and 4, but may be of any of the constructions indicated inthis application. In this case it has been found desirable to secure a deflector plate 96 to the flange 91 of the hub of the rotor, the plate 95 being concentric with the rotor and generally of a diameter slightly larger than the rotor` center ring plate 98. Thus, a portion of the delector plate 96 underlies the annular outlet 99 ofthe classifier rotor.

Also mounted upon the shaft 88 is the fan IGI which is located in' its casing 85 and is arranged of a size and construction to withdraw the mae terial Aof the desired particle size through the classifier, and the annular outlet 92, and also to eject the desired material from the machine to the delivery outlet |52.

The functioning of the classiiier rotor 95, with its tapered skirt |03, is exactly as has been described in connection with the rotor 65. That is to say, the material enters the space defined by the casing 8| where it is free to expand and become picked up in the vortex created and maintained by the rotor 95. The oversize will fall through the bottom of the casing .3| and a substantial part of the oversize vwill be eliminated in the travel of the air-suspended material through the casing 8|. The deilector disc 96 aids in the creation and maintenance of the vortex and also aids in increasing the throwout of material within the area defined by the depth of the skirt |23, thus keeping material from din rectly entering the annular outlet S9. The disc 96 may be varied in diameter according to the difficulties in classifying the material.

In some cases, with material that is difficult to classify, it is advisable to use two rotors, and several variations in the arrangements thereof are illustrated in Figs. 5, 6, '7, and 8.

Referring to Fig. 5, there is shown a classier rotor comprising a hub |06 which nts upon the rotor shaft 25 and has an intermediate flange |07 to vwhich is bolted the center ring plate |08. On top of the' ring plate |88 are mounted the spokes |09 and at the outer extremities thereof is sem cured the outer ring plate I, to dene the annular slot IIE, all as has been described above in connection with Fig. 3. The rotor has a depending outwardly ilared skirt I3 similar to the skirt 'I4 of Fig. 3, except that it will be noted the annular slot is smaller in Fig. 5 and therefore the skirt is longer. Bolted on the underside of the intermediate flange |01 is a ring-shaped disc lill to the underside of which is secured a plurality of the round rod spokes H5, which extend radially outwardly close to the skirt l I3, the outer extremities of the spokes H5 being joined by the hoop I I5.

The number of radial spokes H5 in the lower rotor element also may be selected in accordance with the particle size being delivered from the machine and from the nature and characteristics of the material being classied and, preferably, the number oi spokes in the lower element will be diierent 'from the number of spokes in the upper rotor element. For example, in one embodiment sixty/four spokes have been used in the lower rotor clement operating in conjunction with an upper element having only thirty-two spokes. The relationship may be reversed, and there need not be this diierential in the number of spokes respectively.

The functioning oi the classier rotor of Fig. 5 is, in principle, the same as that described above in connection with Figs. 1 to 4. The addition of the lower or sub-classier rotor element increases somewhat the depth and intensity of the classify- Aing vortex both in the free space below the rotor and within the depth of the rotor skirt H3 but primarily the subclassier rotor with the rounded leading edges and the broad area of its spokes functions to reject oversize particles as described above, after which stray particles will be subjected tothe action between the rotor elements and then to a final combing by the spokes of the upper rotor element. It appears to be desirable to space the upper and lower rotor elements with the upper set of spokes |29 above the skirt H3 and the lower set of spokes H5 above the lower edge of the skirt, that is, in the type illustrated in Fig. 5 where the two rotor elements operate as a unit.

Fig. 6 illustrates the same type of double rotor element as shown in Fig. 5 except adapted for .the classification of materials of low specific gravity and where delivered particles form a substantially impalpable powder. In this case theV classifier rotor comprises a hub |2|, keyed to the shaft 26, a center rotor disc |22 secured to the ilange of the hub, a plurality of round spokes |23 radiating from the disc |22, an outer rotor disc |24 carried at the extremities of the spokes and dening the annular slot |25, and a downwardly and outwardly flared skirt |26, all similar to the same elements in the rotors previously described herein, except for the angle of the skirt and its offset beneath disc |24. In this case, the annular slot |25 is very narrow and is located radially about midway 4between the rotor hub and the outercasing. so that the skirt |26 is considerably deeper than in Fig. 5. The lower or sub-classifier rotor comprises a center disc |21 mounted directly upon. the shaft 26, and of a diameter substantially the same as the center disc |22, and a plurality oi equi-spaced round spokes |28, extending therefrom nearly to the skirt |26, the outer extremities of the spokes being joined by the hoop |29.v Mounted upon the ilange of the hub |2| so as to be intermediate the two rotor elements is a deflector plate |2| which is of a diameter to extend substantially across the vertical projection of the annular slot |25. Thus, centrifugal action has been added in the space between the rotor elements, but primarily the plate functions to cause the air and material to execute a sharp turn toward the skirt I 26 in passing from the first classifier rotor to the second classifier rotor, which deiiecting action has been found effective with a few materials that are especially difficult to keep free from oversize particles.

Fig. '7 illustrates another double rotor classifier unit, for use with material having a large surface-to-weight ratio. The rotor unit here comprises a hub |35, keyed to the shaft 26, a center disc |36 secured to flange |31 of the hub |35, a'

l'l plurality of round spokes |38 radiating from th disc |36 andeiitending close to the inner wall of the casing, and an outer rotor disc |36, secured tospokes |33, all similar to the single-type clasleiner rotors heretofore described. While the rotor discs |36 and |39 denne an annular opening, in .this construction the effective annular outlet slot -|-4| is defined by the center rotor disc |36 on one side and the diaphragm 15B on the other side. vDiaphragm 15B is mounted on the casing 22, and is similar in arrangement and function to the diaphragm l5 of Figs. l and 3.

A second rotor element is bolted to rthe hub yiangev |31, the saine comprising a center rotor lise H3 vcarrying a plurality of the round equispaced'spokes ili and an outer rotor disc M5 which is concentric with disc |43 and spaced .therefrom to define a second annular slot or passagel which may be of the same size and radial location as the outlet slot Uli, but this neednot be adhered to. The length of the spokes |44 and the location of the outer disc |155 are such-that an outwardly flared skirt |41 may be carried thereby, the skirt M1 being parallel with and spaced from the skirt |42, which is suitably secured lto the ring disc |39 or tothe spokes |38 .of the upper rotor |li|. The location of the second rotor element and the spacing of the skirts maybe selected and changed according to the nature of the material, the distance apart of the\` two rotor elements being lregulated by the use of one or more spacer rings |413.

A deector plate lil@ also is mounted. upon the flange |31 of the hub |35 so as to be intermediate the two rotor elements. The diameter of this plate falso is selective and `preferably extends a substantial distance across the projections of the annular slots |1i| and |46. The purpose of the deector plate |i9'is to'orce the material passing through the annular slot M6 to make a sharpv turn around vthe perimeter of the plate |49 in its passage tothe annular outlet slot Ml, and the disc likewise increases the centrifugal throw-out action inthe space between the two rotor elements; The spacing of the plate |49 from the rotor disc |36 is controlled by the size of the spacer ring |5I. Lowering the plate M9 to be closer to the lower rotor disc |43 will increase the velocity of the outward ow of air-suspended material and hence of the throw-out force.

itis 'obvious that with the rotor -construction described in Fig. 7, the vor-tex action in the free spacev below the rotor elements will be of higher velocity, and .that the lower skirt |51 receives its air from the vortex in this free space, directing a current of air voutwardly and downwardly against the wall Yof the casing, and therefore acrossV the space between the lower edge -of Ithe skirt and the casing wall or liner. The upper skirt. |42 receives its air from the area between the two rotor elements and likewise produces a downwardly directed stream of air sweeping `the wall of the casing in the area opposite the ybottoms of the two skirts M2 and |41. The velocity of the air will be aiected by the spacing vbetween the two skirts, and the depth of the free space be` low the rotors may be increased several inches.

It .also will be noted that the round spokes of the two rotor elements `are `above and ybelow the space between the two rotors, further reducing the Ylikelihood of disturbances by the Irotor elements within the space therebetween. This arrangement is optional but desirable, especially sincev .the round spokes idd will not materially affectthe functioning of the vortex in the space thereof the outer ring-shaped rotor disc therebelow.` Also, the number of the `spokes |38 and IM will be selected .in coordination. with the particular annular slot, the .size particles passing therethrough, and the characteristics oi the material being classined. f

Fig. 8 illustrates a construction in which two separate rotors, functioning independently of each other, are used in the classiier space. Such an arrangement as here shownis dictated, for

example, in cases of materials which have a .tendency to rise out of the pulverizing zone beforethey are sufliciently reduced 'in particle size as in the case of certain seeds. In this example, the reference numeral 43B indicates the top lrotor section of a pulverizing rotor such as indicated in Fig. 1 and corresponds to the rotor section '43 thereof, the same being closed at the top by the rotor plate MB. The nrst classifier rotor, indicated at |65, is spaced a few inches above the pulv'erizing Yrotor and comprises a hub |58 keyed to the rotor shaft 26, and a center disc |51 bolted tothe flange l|58 of the hub. The disc |51h'a1s radiating therefrom a plurality of equi-spaced round spokes |55) which carry at the outer-end |61 which together with the center rotor disc |51 deiines the annular slot |62. A depending outwardly flared skirt |63 is secured to the inner edge of the annular slot |62. It will be noted that the classifying rotor |55 is not as large in diameter as the upper classifying rotor, indicated at ld, so that there is a larger annular space between the edge of the rotor |55 and the inner wall of the casing 22.

The rotor indicated at |64 is located at the top of the classier zone and is somewhat similar in construction to the rotor described in yconnection with Fig.y 2, the .same being provided with the radial spokes |65, the ldiscs |66 and L|61 and the flared skirt |66, aswell as the central deiiector plate 113|. In the illustration, the `annular slot |63 is defined by the disc |66 and by the diaphragm ring 15C, the internal diameter of which is less than that of disc |61. Also the angle of the skirt |69 is reduced and the skirt lengthened. 'As with all the other top classifier rotors, the rotor elements, including the skirt, terminate close to the Wall of the casing 22. The free space |13 between the rotors should bey sufficiently large that the rotor actions -do not interfere with each other, and usually a space of iive or six inches is 'suiciena the two rotor hubs being separated by a plurality .of 'sleeves |14. on the shaft 25. In each case, the size and location of the radial slots |62 and |66 and the number ofV small, round spokes |59 and |65 willy 'be selected in accordancewith the principles outlined above. v

The material leaving the pulverizing zone, Viz. the annular space indicated at |15, will be drawn upwardlyy by the ian |16 and pass through the annular slot It into the free space |13'. The classier rotor |55 will function to eject most of the Voversize material by reason of the vortex action between the flat pulveriZi-ng rotor plate 41B and the classifier rotor |55 and also within that rotor., as well as by the action of the spokes F59. This oversize material will be thrown to the wall of the casing 22 where its speed will be retarded so that it can fall back intothe pulveriain'g Zone, as explained above. The latter action is aided by the stream of air directed downwardly from the flared skirt |63, which downward current of air meeting the air-suspended material as it leaves the pulverizing zone the top of the rotor.

serves to introduce a factor which must be overcome by the rising material, so that in a substantial measure insufliciently pulverized material is prevented from lleaving the pulverizing zone.

Whatever material passes the annular slot |62 and the spokes |59 enters the free space |13 and is there subjected to the vortex action set up in that space by the rotors |55 and |64 operating at the top and bottom thereof. Hence, oversize material which escaped the action of rotor |55 is ejected as it proceeds through this vortex. Material making its way to the passage |68 is then subjected to the action of the upper rotor |64, including the action of the denecting plate I1| and the spokes |55, so that all stray oversize particles are removed from this diicult-to-classify material before the material gets out of the classifying chamber. The skirt |69 of the upper rotor H54 functions as heretofore ,described for the single rotor, directing a current of air downwardly along the casing wall to prevent oversize particles `from escaping over The rotor |55 is of smaller diameter than the .rotor |64 so thatthe rotor actin will notv interfere with thev return of the oversize material from the free s acey |13 into the pulverizing zone |15.

This` arrangement of two independently operating rotors functioning in series with each other is very effective, too, in classifying material of extremely fine particle sizes.

Figs. l to 13 represent other embodiments of classifier rotors using the round spokes in the rotor which may be used in some applications. Fig. l0 is the simplest embodiment showing a hub |8| which is to be keyed to the rotor shaft 26. The flange |82 on the hub carries a disc |83 on Which 'are mounted a plurality of radial spokes |84 which are round and equi-spaced and small. in'diameter and extend substantially to the wall of the casing 22, as above described.. An'annular outlet' slot |35 is defined by a rotor disc |85 also secured to the flange |82 and a diaphragm ring- |81 mounted upon the wall of the casing 22. As in the previous instances, the number of spokes, and the size and locationof the annular slot, will be chosen'in accordance with the particle size being selected and the nature and character of the material being acted upon. This form of'classiiier willl have only a few practical applications.

Fig. ll indicates the rotor of Fig. with a sealing arrangement added which will counteract the tendency of oversize particles to get into the outlet |85 over the top of the classifying rotor without passing therethrough. This sealing arrangement consists of a ringl plate ist mounted on top of the spokes |84 in the area beneath the diaphragm ring |81, A number of short lengths of the round spokes, indicated at i239, are secured on top of this ring plate |88 to operate in close running clearance to the diaphragm |81. The inner edge of the diaphragm |81 is provided with the downturned collar 49| which extends into yclose running clearance with the spokes |S4 and with the inner edges of the ring plate 33 and blades |89 on top thereof. The plate lll keeps material from passing between the spokes Hifi in the area beneath the diaphragm |81, and the .blades |39 act as fan blades to prevent the entry of material in the space above the rotor, while the collar |9| additionally serves to sealnoii this possible entrance against unwanted oversize material passing into the outlet |85.

Fig. l2 is a View similar to Fig, l1 except for the addition of a-sub-classifier rotor'element comprising the center' .disc 92 secured beneath the flange HB2-of the hub |8|, and carrying radiating thereirem aplurality-of the round spokesy |93 which extend across the vertical projection of the annular outlet but apparently do not need to extend .as close to the cylinder 22 as the spokes E84 of the upper rotor element. Since the two rotor elements are fastened onthe same hub they function somewhat as a unit but in the arrangement of Fig-l2, it is preferred thatthe spokes v|93 of the lower rotor element be physically located to appearl in the .spaces between the rotor blades |84 of the upper rotor element, asindicated in Fig. 13. Thus, as the double rotor rotates, and acts somewhat as a rotary screenthere is much more likelihood of any stray oversize particles being struck by the rotor spokes and .deflected away from the annular outlet. |35. Again, the number of spokes ineach rotor will be chosen according to the delivered particle size andthe characteristics ofthe material. d

We have indicated variousl constructions of mechanisms, and the applications thereof, from which it will be apparent 'that the assembly of a machineto suit a particular set of conditions can be accomplished readily by bringing together units having features especially adapted forthe most eiicient pulverization Aand classification of the particular material ibeingzprocessed. Hence, it may be said that the'features disclosed herein may be used independently of each other While,r

across saidA outlet, vand adependingoutwardly v flared annular skirt on said rotor, and extending from approximately the outer edge yof saidl annular outlet, a plate mounted on said shaft spaced from Asaid spokes and' extending radially to be partially` alignedwith said outlet, andmeansfor setting up an air current to `withdraw sufcient pulverized material through said outlet, while the rotor and plate cause rejection of oversize `material in said casing.

2. In a classifier for air-suspended pulverized material, a cylindrical casing, an opening in the lower part of said casing for admitting air-suspended pulverized material, a diaphragm ring at the top of said casing, a rotor mounted in said casing and operating adjacent said diaphragm and comprising a hub, a at center disc secured thereto, a plurality of equi-distant, round spokes radiating from said disc and extending substantially to the wall of the casing, a at ring plate carried by said spokes so as to be concentric with and spaced from said center disc whereby to define an annular opening with the radial spokes extending thereacross, a depending outwardly flared annular skirt carried by said rotor in position to direct air therefrom downwardly :along the wall of the casing, a second group of radial, equidistant, round spokes carried by said hub so as to be spaced vertically from the first mentioned spokes, a depending outwardly flared annular skirt carried by the second set ofv spokes :and spaced from the rst mentioned skirt, the two groupsl of spokes being adjustably mounted for vertical displacement whereby to change the spacing therebetween and between said skirts, a delector plate carried by said hub and extending radially between said annular openings, and means for setting up an air current to withdraw suciently pulverized material through said annularv openings and past said deector plate, while the rotor and parts carried thereby cause rejection of oversize material in said casing.

3. In a classifier for air-suspended pulverized material, a cylindrical casing, an opening in the lower part of said casing for admitting air-suspended pulverized material, a diaphragm ring at the top of said casing, a free space therebelow, a shaft extending through Said `space, a pair of rotorsk mounted thereon, each rotor comprising a hub, a ilat center disc secured thereto, a plurality of equi-distant round spokes radiating from said disc, a :dat ring plate carried by said spokes so as to be concentric with and spaced from said center disc whereby to deline an annular opening -with the radial spokes extending thereacross, a 'depending outwardly ared annular skirt carried by each rotor in position to direct air therefrom downwardly along `the wall of the casing in the area immediately therebelow, one of said rotors operating adjacent said diaphragm and being of larger diameter, and the other of said rotors being spaced from the rst mentionedr rotor and operating near the bottom of said free space, and means for setting up an air current to withdraw sui'liciently pulverized material through Said annular openings in succession, while their-otors cause rejection of oversize material in said casing.

4. In a classifier vmechanism for pulverized materials, a, casing having an outletv at onev end thereof, diaphragm means mounted on said casingv and extending inwardly to define one side 5. In a classifier mechanism for pulverize'd materials, a casing having an outlet :at one end thereof, diaphragm means mounted onsaid cas,- ing and extending inwardly to denne one side of said outlet, a rotor for operation in said casing and comprising a hub portion, va disc extending outwardly from the hub and forming with said diaphragm an annular outlet, a series of round spokes radiating from said hub and extending along one side of said vdiaphragm and adjacent thereto and to said casing, and outwardly ared skirt means depending from said rods and terminat'ing adjacent said casing, a second rotor defining .a second annular outlet in said casing and spaced from the first mentioned rotor, a material delecting plate extending at least part way into the path between said outlets,`and means for feeding air and material to said casing and withdrawing selected material through said outlets. Y

'HENRY G. LYKKEN.

WILLIAM H; LYKKEN.

y REFERENCES CITED The following references are of record in the file of this patent:

f UNITED sTA'rEs PATENTS Number Name Date Re. 20,543 Crites Nov. 2, 1937 227,064 Sewell Apr. 27, 1880 255,890 Sharpneck Apr. 4, 1882 321,108 Hogeboom'et al. June 30, 1885 525,095 Detwiler Aug. 28,1894 1,783,357 Cook Dec. 2, 1930 1,958,816 Gibson May 15, 1934 2,108,609 OMara Feb. 15, 1938 2,169,680 Crites Aug. 15, 1939 2,200,822 Crites May 14, 1940 2,294,921 Lyk-ken Sept; 8, 1942 2,304,264 Lykken Dec. 8, 1942 2,329,900 Hermann Sept. 21, 1943 2,350,737 Eiben June 6, 1944 FOREIGN PATENTS Numberl Country Date 316,901 Germany Dec. 13, 1919 340,866 Germany Sept. 20, 1921 397,096 Germany June 16, 1924 399,102 Germany July 19, 1924 413,585

Great Britain July 19, 1934 

